Flash welding method

ABSTRACT

Apparatus for and method of flash welding the trailing and leading ends of elongated metal strip, particularly where the strip is in coil form. The flash welder may be of standard construction with the exception that a shear is built into the welder and disposed downstream of the welding clamps, and a strip indexing means is disposed downstream of the shear. Strip from one coil is fed through the welder without obstruction. When the supply on this coil is near exhaustion, further movement of the strip is arrested and the shear is operated to sever the strip. The tail portion of the severed strip is withdrawn from the welder and when such portion clears the welding clamps, a gauge bar is disposed between the clamps while the main portion of the severed strip is moved in an upstream direction by the indexing means so that its sheared end abuts against one side of the gauge bar. Strip from the other coil is fed into the welder until its leading end abuts the opposite side of the gauge bar. The welding clamps are then closed on the strips, the gauge bar is withdrawn, and a normal flash welding operation takes place.

United States Patent [191 Williams et al.

11 3,771,215 NOV. 13, 1973 1 FLASH WELDING METHOD [75] Inventors: ArthurL. Williams, Warren; Robert S. Ellis, Canfield, both of Ohio [73]Assignee: Wean United Inc., Youngstown,

Ohio

[22] Filed: Mar. 30, 1972 [21] Appl. No.: 239,588

Primary Examiner'Robert Baldwin Assistant Examiner-Robert J. CraigAttorneyMichael Williams [57] ABSTRACT Apparatus for and method of flashwelding the trailing and leading ends of elongated metal strip,particularly where the strip is in coil form. The flash welder may be ofstandard construction with the exception that a shear is built into thewelder and disposed downstream of the welding clamps, and a stripindexing means is disposed downstream of the shear. Strip from one coilis fed through the welder without obstruction. When the supply on thiscoil is near exhaustion, further movement of the strip is arrested andthe shear is operated to sever the strip. The tail portion of thesevered strip is withdrawn from the welder and when 5 Claims, 6 DrawingFigures PATENTEDNUV 13 I973 SHEET 10F 2 Nmil.

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PATENTEDNDV 13 ms SHEET 2 [IF 2 6 9m 0 J vm J vwE VMQ l d uI Q l \CFLASH WELDING METHOD BACKGROUND AND SUMMARY In order for industry tocombat rising costs, greater emphasis is being placed on increasedproductivity. In a continuous steel mill line operation, speed of thesteel strip advancingalong the line has been increased, but a limitingfactor has been the welding of the trailing end of strip from one coilto the leading end of strip from another coil.

Our invention reduces time limitations involved in the use of standardflash welders for joining strip from coil to coil, without materiallychanging standard flash welder design. Briefly, a shear is built intothe flashwelder and positioned downstream of the welding clamps. Whenthe strip supply from one coil is near exhaustion, movement of suchstrip is halted and an indexing device downstream of the shear graspsthe strip while the shear severs it transversely. The tail end of thesevered strip is withdrawn from the welder, and when such tail endclears the welding clamps, the grasped portion of the strip is movedupstream to abutment with one side of a gauge bar, while the leading endof strip from another coil is fed into the welder to abutment theopposite side of the gauge bar. The welding clamps are then closed onthe strips, the gauge bar withdrawn, and normal flash welding takesplace.

DESCRIPTION OF THE DRAWINGS In the drawings accompanying thisdescription and forming a part of this specification, thereare shown,for purposes of illustration, several embodiments which our inventionmay assume, and in these drawings:

FIG. 1 is a side view of a flash welder embodying our invention, partsbeing broken away and parts fragmentarily shown,

FIG. 2 is a fragmentary view of a different strip indexing means whichmay be used in the embodiment shown in FIG. 1, and

FIGS. 3 through 6 are schematic views showing the position of partsduring the various steps in the operation of the embodiment shown inFIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The flash welder shown in FIG. 1may take the form shown in U.S. Pat. No. 3,003,052, which is assigned tothe assignee of the present application. The welder comprises pairs ofstrip clamping jaws 12 and 13 which extend transversely of the strip S(shown in dot-dash lines). Each jaw pair comprises relatively movableupper and lower jaws which may be closed on the strip by suitable fluidcylinders. The jaw pair 12 is carried by a stationary part 14 of thewelder frame, while the jaw pair 13 is carried by a movable part 15 ofthe welder frame. In accordance with standard design, the-frame part 15is moved toward and away from the stationary part by a suitable fluidcylinder, and thus providescorresponding movement of the jaw pairs 12and 13 for the flash welding operation.

The strip S is fed from a coil Cl which is mounted on a standarduncoiler 16 driven by a reversible motor. A second coil C2 is disposedadjacent the coil C1 in a manner shown in patent 3 256 419 which is alsoassigned to the assignee of the present application. The coil C2 ismounted on a similar standard uncoiler 17 which is driven by areversible motor. The strip S1 (shown in dash lines) from the coil C2 isfed over an idler roll 18 and its leading end is held by clamps 19 instand-by position relative to the welder. An entry shear 20 may bedisposed adjacent to the clamps l9 and is operable to crop the leadingend of the strip from coil C2 so that such end is ready for the weldingoperation. Similar clamps 21 are disposed for cooperation with theleading end of the strip S together with an entry cropping shear 22.

Strip S moves through the open clamps 21 and shear 22 and through a pairof rolls 23 which position it along the pass line of the welder. In thepresent case the rolls 23 are merely idler rolls, although these rollsmay be driven by a reversible motor, in which case the uncoilers 16 and17 need not be driven.

A built-in shear 25 is supported by the stationary frame part 14 inposition downstream of the pairs of welding jaws 12, 13. A fluidcylinder 26 is connected to the movable blade of the shear and isoperable to cause the shear to transversely sever the strip.

A gauge bar 27 is carried by the stationary part 14 of the welder frameand may take the form shown in U.S.

Pat. No. 3,257,060, also assigned to the assignee of the presentinvention. A fluid cylinder 28 is operable to move the gauge bar 27vertically, so that at a predetermined time its lower end may bedisposed betwen the pairs of welding jaws 12, 13.

If desired, strip trimming and notching devices 30, 31 may be supportedby the bed of the welder, downstream of the shear 25. The trimmingdevice 30 may correspond to the construction shown in FIG. 2 of U.S.Pat. No. 3,003,052, and generally it comprises means for trimming weldproturberances which project from the opposite flat sides of the stripat the weld joint. The notching device 31 may correspond to theconstruction shown in FIG. 3 of U.S. Pat. No. 3,003,052, and generallyit comprises means for trimming weld proturberances which project fromopposite side edges of the strip at the weld joint.

Further, if desired, an annealing device 32 may be positioned downstreamof the notching and may comprise any suitable means for annealing theweld area. Although the trimming, notching and annealing devices are notessential insofar as the invention is concerned, they are included inthe interest of disclosing a complete system of welding and treating theweld area.

.A strip indexing means 33 is disposed downstream of the welding jawsand in the disclosed embodiment, such means is downstream of andadjacent to the annealing device 32. In FIG. 1, the indexing means isshown in the form of a pinch roll stand which is secured to orpositioned adjacent the left hand end of the table which supports theannealing device 32 and other parts of the welder. The stand comprises apair of pinch rolls 34, the upper one of which is forced toward thelower one by a fluid cylinder 35 to pinch the strip S therebetween. Oneor both of the rolls 34 may be driven in a measured-type roll rotation,in accordance with known practice, to effect accurate dis-position ofthe strip along the pass line.

In FIG. 1, it is assumed that the strip S is moving cessing mechanism,or a combination of these strip moving means.

When the supply of strip on the coil C1 nears exhaus tion, movement ofthe strips is halted in any suitable manner. This may be accomplishedmanually by the operator following visual observation of the dwindlingsupply of strip on the coil, or it may be accomplished automatically bymeans of a limit switch which is responsive to the decrease in diameterof the strip on the coil C1.

Substantially with the halting of strip movement, the pinch rolls 34,34of the indexing means 33 are engaged on the strip, as seen in FIG. 3, tograsp the same and hold it against movement. To engage the rolls on thestrip, a valve controlling fluid flow to the cylinder 35 may be actuatedby the same means that causes halting of the strip movement.

By means of a suitable time delay, the fluid cylinder 26 is operated tocause the shear 25 to go through a cutting cycle and then return to itsinoperative position. Operation of the shear 25 will transversely severthe strip S into two portions, the main portion being downstream of theshear and grasped by the rolls 34,34 of the indexing device 33, and thetail being upstream of the shear and integral with the small amount ofstrip remaining on the coil C1.

Immediately after the strip S has been severed by the shear, the tailportion is started to be withdrawn from the welder, either by reversalof the motor for the uncoiler 16, or by reversal of rotation of thepinch rolls 23, and this may be effected by an electrical control whichis activated at the time the shear has completed the cut and returned toinoperative position. When the withdrawing tail portion has cleared thewelding jaws or clamps 12, 13, as seen in FIG. 4, the fluid cylinder 28is activated to dispose the lower end of the gauge bar 27 between thepairs of welding jaws. Activation of the cylinder 28 may be effected bya valve which is electrically energized by a limit switch or electriceye responsive to the position of the strip tail end when it clears thewelding jaws.

At about the same time the tail end of-the strip is starting itswithdrawal movement, the drive to the pinch rolls 34,34 is activated tocause rotation of the rolls in the direction of the arrows shown in FIG.4. This drive may be effected by a control which receives a signal fromthe strip withdrawing means. Rotation of the pinch rolls 34,34 will movethe main strip portion upstream until the sheared end of this portionabuts against the facing side of the gauge bar, and further movement inthis direction will then be halted, such as by a revolution counter onthe rolls 34,34, or by a limit switch in the path of movement of thesheared end. The pinch rolls 34,34 of the indexing means 33 remainclamped on the main portion of the strip S.

After the tail portion of the strip has cleared the rolls 23, the motorfor the uncoiler 17 is energized, and thus may be accomplished by alimit switch which is tripped as the sheared end of the tail portionmoves to the right of the rolls 23. Simultaneously with the energizationof the uncoiler motor 17, the clamps 19 are opened and the strip S1 isfed to the rolls 23, a suitable guide (not shown) being utilized toproperly direct the end of this strip to pass between the rolls. Thestrip S1 is fed into the welder until its cropped end abuts the oppositeside of the gauge bar 27, and is then halted in any suitable manner,such as by activation of a limit switch.

With the strip ends abutting opposite sides of the gauge bar, thecylinders for the welding jaws 12,13 are activated to close the jaws onsuch strip ends, and the cylinder 20 is then activated to withdraw thegauge bar end from between the welding jaws, as shown in FIG. 6. Thewelding jaw cylinders may be actuated by limit switches activated whenboth strip ends have abutted the gauge bar 27. When the welding jaws arefirmly clamped on the strip ends, a signal is given to the weldercontrol to cause it to perform a normal welding operation to join thestrip ends. Such signal may result from pressure switches responsive tothe pressure built up in the clamping cylinders.

During the time the foregoing sequence is taking place, a new coil ofsteel may be disposed on the uncoiler 16, with its leading end croppedby the shear 22 and held by the clamps 21, as seen in FIG. 6, ready foruse when the strip supply on the coil C2 nears exhaustion.

The pinch rolls 34,34 of the strip indexing means 33 have remainedclamped on the main portion of strip S and when the weld has beencompleted, and the welding jaws opened, the pinch rolls 34,34 areimmediately rotated in the direction of the arrows shown in FIG. 6 tomove the welded strip downstreamof the pass line. The motor for rotatingthe rolls 34 may be activated by a signal from the welder following thewelding operation, such as a pressure switch responsive to the decreasein pressure in the welding jawcylinders.

The first amount of rotation of the rolls 34,34 in the direction of thearrows in FIG. 6 will be a measured,

predetermined amount, which may be controlled by arotation counter, tomove the welded strip downstream until its weld line is accuratelyaligned with the centerline 40 of the trimming device 30. When soaligned, and with the strip halted since it is still gripped by the nowstationary rolls 34,34, the trimming knives of the device 30 will becaused to move across the upper and lower sides of the strip to trimweld protuberances therefrom.

After the trimming operation, the rolls 34,34 are again rotated aprecise amount in the direction of the arrows shown in FIG. 6 to movethe welded strip downstream to precisely align the weld line with thecenterline 41 of the notching device 31, and the latter is thenactivated to trim weld flash from the opposite side edges of the haltedstrip. After edge trimming, the rolls 34,34 are again rotated a preciseamount to accurately align the weld line with the center line 42 of theannealing devide 32, and the weld area is annealed.

After annealing, the cylinder 35 of the indexing means 33 is activatedto open the rolls 34,34 and the strip is free to move from the coil C2along the pass line, to the strip processing line.

DESCRIPTION OF OTHER EMBODIMENT Instead of the pinch roll stand 33 abovedescribed, a transfer carriage 50, shown in FIG. 2, may be employed toindex the strip to the various positions. The transfer carriage is shownand described in US Pat. No. 3 003 052, as is a control circuit foreffecting its operation.

Briefly, the transfer carriage 50 is mounted for movement along rails 51in a direction parallel with the movement of the strip along thepassline of the welder. The carriage has a pair of clamps 52,52, theupper one of which is moved toward the lower one by a fluid cylinder 53to clamp the strip therebetween.

FIG. 2 shows the transfer carriage in position, with clamps open, whenthe strip is moving freely along the pass line. When the supply of stripon coil Cl nears exhaustion, the clamps 52,52 are engaged on the strip.After the strip is cut transversely by the shear 25, the main portion ofthe strip is moved toward the welding clamps 12,13 by movement of thetransfer carriage to the right, as by means of a fluid cylinder 54,until the sheared end of such strip abuts against the gauge bar 27.After welding, the transfer carriage moves to the left in preciselycontrolled amounts, to accurately align the weld line successively withthe devices 30,31 and 32, for such devices to operate on the strip asbefore described, and thereafter the carriage clamps 52,52 are opened topermit free movement of the strip along the pass line. We claim:

1. The method of welding the trailing end of strip from a first coil tothe leading end of strip from a second coil in a flash welder having theusual pairs of welding clamps, each pair being adapted to engage opposedsurfaces of the ends of respective strips and-the pairs of clamps beingmovable toward and away from each other, the welder also including agauge bar movable between the pairs of clamps and having opposite sidesagainst which strip ends are abutted for welding spacing, the welderalso including a shear downstream of the welding clamps and indexingmeans downstream of said shear and adapted to engage strip from saidfirst coil and move it toward and away from said welding clamps, theimproved method comprising:

uncoiling strip from said first coil and feeding it along the pass lineof the welder during the time said welding clamps, said shear and saidindexing means permit free movement of the strip,

arresting movement of the strip from said first coil when the supply onsaid first coil nears exhaustion, engaging said indexing means onto thestrip from said first coil to hold the same against movement,

operating said shear to transversely sever the strip from said firstcoil and then return to open position, whereby such strip is cut intotwo portions, one portion held stationary by said indexing meansdownstream of said shear and the other portion freely movable along saidpass line, withdrawing said other strip portion through the pairs ofwelding clamps and out of said welder,

moving said gauge bar, when said other strip portion has been withdrawnsufficiently to clear said welding clamps, to position between saidpairs of clamps,

operating said indexing means to move said one strip portion upstreamuntil its sheared end abuts against the facing side of said gauge bar,

moving the leading end of the strip from said second coil along saidpass line until it abuts against the opposite side of said gauge bar,engaging respective pairs of welding clamps on the strips on oppositesides of said gauge bar, and

withdrawing said gauge bar from position between said clamps and flashwelding the strip ends that have been spaced by said gauge bar.

2. The method according to claim 1 and further including the step ofcropping the leading end of the strip from said second coil prior to thetime it is moved along said pass line, whereby to provide a sheared endfor abutment with the opposite side of said gauge bar.

3. The method according to claim 1 wherein said indexing means is in theform of pinch rolls of the type having measured rotating operation.

4. The method according to claim 1 wherein said indexing means is in theform of a transfer table.

5. The method according to claim 1 and further including the step ofrotating said first coil in a winding direction to withdraw said otherstrip portion through said pairs of welding clamps.

1. The method of welding the trailing end of strip from a first coil tothe leading end of strip from a second coil in a flash welder having theusual pairs of welding clamps, each pair being adapted to engage opposedsurfaces of the ends of respective strips and the pairs of clamps beingmovable toward and away from each other, the welder also including agauge bar movable between the pairs of clamps and having opposite sidesagainst which strip ends are abutted for welding spacing, the welderalso including a shear downstream of the welding clamps and indexingmeans downstream of said shear and adapted to engage strip from saidfirst coil and move it toward and away from said welding clamps, theimproved method comprising: uncoiling strip from said first coil andfeeding it along the pass line of the welder during the time saidwelding clamps, said shear and said indexing means permit free movementof the strip, arresting movement of the strip from said first coil whenthe supply on said first coil nears exhaustion, engaging said indexingmeans onto the strip from said first coil to hold the same againstmovement, operating said shear to transversely sever the strip from saidfirst coil and then return to open position, whereby such strip is cutinto two portions, one portion held stationary by said indexing meansdownstream of said shear and the other portion freely movable along saidpass line, withdrawing said other strip portion through the pairs ofwelding clamps and out of said welder, moving said gauge bar, when saidother strip portion has been withdrawn sufficiently to clear saidwelding clamps, to position between said pairs of clamps, operating saidindexing means to move said one strip portion upstream until its shearedend abuts against the facing side of said gauge bar, moving the leadingend of the strip from said second coil along said pass line until itabuts against the opposite side of said gauge bar, engaging respectivepairs of welding clamps on the strips on opposite sides of said gaugebar, and withdrawing said gauge bar from position between said clampsand flash welding the strip ends that have been spaced by said gaugebar.
 2. The method according to claim 1 and further including the stepof cropping the leading end of the strip from said second coil prior tothe time it is moved along said pass line, whereby to provide a shearedend for abutment with the opposite side of said gauge bar.
 3. The methodaccording to claim 1 wherein said indexing means is in the form of pinchrolls of the type having measured rotating operation.
 4. The methodaccording to claim 1 wherein said indexing means is in the form of atransfer table.
 5. The method according to claim 1 and further includingthe step of rotating said first coil in a winding direction to withdrawsaid other strip portion through said pairs of welding clamps.